Electrical contact



Oct, 13, 1942. w. T. ALLEN 2,298,999

ELECTRICAL CONTACT Filed Aug. 3 1940 lNVENTO/f A TTORNE Y at... Oct. 13,1942 azoaaos amc'rmcu. com'sc'r Wallace '1. Allen, Royal Oak, Michauignor to Square D Company, Detroit, Mich a corporation of MichiganApplication August 3, 1940, Serial No. 350,859

3 Claims. (Cl. 209-186) This invention relates to electrical contactsand more. particularly to electrical contacts having non-weldingcharacteristics.

The object of the invention is to provide a relatively non-weldingelectrical contact having an improved construction for readily securingit to a conducting support.

Other objects and features of the invention will be readily apparent tothose skilled in the art from the specification and appended drawing 11-lustrating certain preferred embodiments in which:

Figure 1 is a side elevational view of a cooperating pair of contactsembodying the present invention.

Figure 2' is a perspective view or a contact according to the presentinvention.

Figure 3 is a sectional view of the contact taken on the line IIIIII ofFigure 2.

Figure is a sectional view of the contact similar to Figure 3, butshowing the soldering material as disposed over th entire back surfaceor the contact.

Referring to Figure l, a pair of cooperating contact elements I and 2for making and breakin an electrical circuit are shown securedrespectively to contact supporting arms 3 and t. The contact elements Iand 2 are of similar construction and according to the present inventioncomprise a body portion 5 having a corrugated back surface, thecorrugations being formed of a series of transverse and. longitudinallyaligned truncated pyramidal formations 5 for a purpose to be hereinafterdescribed.

To avoid a welding together of the cooperating contacts which wouldforce a discontinuation of operation of the electrical instrumentalityat which the contacts ar to form a part, the contacts are composed oi amixture of silver and a relatively highly refractory material such asmolybdenum, tungsten or the like. t has been found that a mixturecomprising thirty-five to fifty-five percent by weight of silver withthe balance of molybdenum or tungsten, with or without a minorpercentage of carbon, provides a satisfactory contact element havingrelatively non-welding characteristics.

The contact element may be molded into the desired shape from a powderedmetai mixture, r the refractory metal, in porous forgo, may b impregnated with the silver. Applicant makes no claim herein to theprocess of making the contact as this forms no part of this invention.Nor is any particular manner of forming the element material oiessential to the present invention, as it is contemplated that it may beformed by any of the common and well known methods now in existence. I

The contact element is secured to its arm by brazing by means ofresistance welding similar to spot welding. Applicant's invention liesin producing a contact element so constructed as to facilitate thebrazing of the element to its supporting arm. The back surface of thecontact element, as above described, comprises a series oi. transverselyand longitudinally aligned truncated pyramidal elevations. Thisconstruction provides a multitude of hot points or areas at which thewelding current is concentrated to produce a relatively high heat toinsure the proper bonding of v the contact to its support.

The bonding material used in brazing the con tact to its supporting armmay be either free silver or one of the well-known silver solders suchas Gil-Foe" which has an approximate composition or 89% silver, 15%copper and 5% phosphorous. This bonding material may be disposed uponthe back contact surface in the recesses, as at l in Figure 3, or it mayalso be disposed to overlap th truncated pyramidal formations, as shownat e in Figure 4.

While certain preferred embodiments of this invention have beenspecifically disclosed, it is understood that the invention is notlimited thereto, as many variations will be readily apparent to thoseskilled in the art and the invention is to be given its broadestpossible interpre tation within the terms of the following claims.

What is claimed is:

i. An electrical contact adapted to be brazed a conducting support,comprising a body portion, or a refractory material having a surface ofthaving a plurality of localized heating areas raised from the main.body portion, surface having a bonded coating oi a fusible bondingmaterial, at least the said points or areas, said coating born appliedto said contact before the brazing operation to form therewith a unitaryarticle adapted to be subse quentiy applied to said support and brazedthere to with the coating forming the bonding medium.

2. An electrical contact adapted to be brazed. to a conducting support,comprising body per tion. formed or silver 35% to 55% refractory thegroup tmzgsten-molybdenwn 45% to the surface of said contact adapted forattachment to the support having a plurality of localized heating pointsor area-s raised from arts between with a fusible bonding material ofthe group silver-silver, solder, said bonding material being applied tosaid contact before the brazing operation to form therewith a unitaryarticle adapted to be subsequently applied to said support ando denum45% to 65%, the suriace oi said contact adapted for attachment to thesupport, having a plurality of localized heating points or areas raisedfrom the main body portion, said surface being flooded over its entirearea including said heating points or areas, with a fusible bondingcoating of free silver, said coating being applied to said contactbefore the brazing operation to form therewith a unitary article adaptedto be subsequently applied to said support and brazed l0 thereto withthe coating forming the bonding medium.

. WALLACE T. ALLEN.

